The speaker stands frozen while an angry person closes in, step by step. The poem counts the approach ("one step closer, two steps closer"), which stretches the moment out and makes the threat feel slow and unavoidable. Details like rolled fists, red eyes and hissing breath make the other person seem less like a human and more like a force of nature, an earthquake in motion.
What the speaker feels is a mix of terror and rising anger. They are so tense they might "vomit or implode." The line "a rib cracks. a bone snaps" is ambiguous: it could be physical violence, or it could describe the speaker's inner collapse under pressure. Either way, the blood "boiling" inside them drowns them from within, as if their own rage and fear are choking them.
The ending turns quiet. The heart whispers "not again, not ever again," which suggests this has happened before, and that the speaker is deciding it must stop. The mood is tense and suffocating, then resolved and shaken.